This invention relates in general to spring handling devices and in particular to a new and useful spring cramp for large helical springs.
In a prior art spring cramp of this kind (U.S. Pat. No. 3,256,594) the spindle head is rotatably applied, by means of an annular flange, and near the rim of the central bore, against the outside of the pressure plate at the spindle head side, and, with the pressure plate at standstill, the spindle can rotate. The pressure plate which is secured to the threaded tube and also has a central bore, is non-rotatably connected to the pressure plate through two diametrically opposite radial fingers which engage between pins provided on the outside of the pressure plate and at the same time apply against the rim of the central bore. The pressure plates have recesses allowing the radial fingers of the threaded tube to pass through. Since there is no security against rotary motion, so that the two pressure plates can freely rotate relative to each other and be prevented therefrom only by the friction between the threads, such prior art cramps cannot be employed in practice, for reasons of safety. Experience has shown that due to the pitch of the springs, the two pressure plates, and the spindle and threaded tube along therewith, may automatically start turning, and unscrew the spindle from the threaded tube, so that the spring becomes free in an uncontrolled manner. This cannot be remedied by a left-hand spindle, because this would lead to another hazard of giving the spindle a wrong direction of rotation, again with the dangerous consequences.